I. Field of the Invention
The invention pertains to piping consisting of individual pipe sections of rectangular cross-section connected by flanges.
II. Description of the Prior Art
Heretofore individual pipe sections consisted of sheet metal having connecting flanges at each end which are in the shape of a frame and of an angular profile. The flange frame consists of four rods which are mitre-cut, angular profiled, and joined to each other by welding.
Manufacture of these well-known flange frames from welded angular rods requires considerable expenditures in view of the fact that the side pieces of the flange frame, which are perpendicular to the walls of the individual pipe section, must have a surface which is suitable for tightly joining two adjacent individual pipe sections. For this reason the welding must be carried out with special care. Additionally, welding invariably causes some distortion at the weld location necessitating a post finishing operation at the surface of the flange frame which is to provide the tight seal.
Because of these inherent disadvantages in the manufacture of flange frames for rectangular cross-section piping, new methods have been searched to obtain a flange frame for which the welding operation is no longer required. To form such a frame, a hollow section is used; characterized by a linear side leg which lies alongside the interior wall of the individual pipe section and has another side leg which is vertical to the first and provides the sealing surface of the flange frame. The latter side leg is bent back parallel to the interior side leg, forming a slot, into which the wall of the individual pipe section can be inserted. Four pieces profiled in this manner are cut to the respective lengths of the rectangular sides of the pipe section, slipped onto the four side walls, and fastened there. The free corners are then covered by four angular corner pieces so that in the end a flange frame is provided which completely encircles the pipe. The angular corner pieces are provided with perforations used for the joining of two adjacent pipe sections. This familiar design of a flange frame indeed makes the welding superfluous and, thus, avoids the above-mentioned disadvantages, but is instead complicated in structural features, requires considerable expenditure in manufacturing the individual components, and requires a considerable assembly effort. In addition, such a composite flange frame requires the sealing of the locations where the vertical and horizontal side pieces are joined by the angular corner pieces, otherwise no tight seal can be guaranteed between individual pipe sections.